A variety of devices and methods are known for the enteral, parenteral or oral delivery of beneficial agents, such as nutrients, medicaments, probiotics, diagnostic agents and marker dyes, to a patient. For example, it is well known to feed a fluid, such as a liquid enteral nutritional product, by gravitational or positive flow from a hangable bottle or bag having an outlet connected to a drip chamber which, in turn, is connected to a flexible tubing or lumen leading to a nasogastric tube or a feeding tube inserted through a gastrostomy or a jejunostomy to a patient. The liquid enteral nutritional product may be aseptically processed or terminally retorted, and may be supplied in a pre-filled, ready-to-hang container, or placed in such a container by a caregiver. However, the selection of diets, particularly special diets, from amongst the rather modest number of typically available liquid enteral nutritional products that are currently available is rather limited.
Moreover, it is often desirable to administer simultaneously a variety of beneficial agents, such as nutrients, medicaments, probiotics, diagnostic agents and marker dyes. These various ingredients, however, often are not stable during heat sterilization and may not be mutually compatible with other desired ingredients for an extended period of time, such as days or even months until used. As such, the combination of these beneficial agents are not readily amenable to large scale preparation and consequent storage as the product moves through commerce.
It also is beneficial to make the liquid enteral nutritional product more detectable in a patient after delivery, such as for diagnostic purposes and to identify when the enteral nutritional product is improperly fed to an area external to the stomach or intestines. One such method of making the liquid enteral nutritional product more detectable is to dissolve a suitable physiologically acceptable marker dye into the liquid product. Because compatibility of such marker dyes with other beneficial agents must be considered, it is advisable not to introduce the marker dye prior to heat sterilization or extended storage.
For these reasons, it therefore has been desirable to alter, modify or mark nutritional products during enteral tube feeding into the gastrointestinal tract of a patient. Certain new apparatus and methods have been developed to address these needs, and are the subject of several recent patents, including U.S. Pat. No. 5,531,681, U.S. Pat. No. 5,531,682, U.S. Pat. No. 5,531,734, U.S. Pat. No. 30 5,533,973, U.S. Pat. No. 5,549,550, U.S. Pat. No. 5,738,651, U.S. Pat. No. 5,741,243, U.S. Pat. No. 5,746,715, U.S. Pat. No. 5,755,688, and U.S. Pat. No. 5,755,689. Generally, these patents are directed to various aspects of apparatus and methods, which use a formulation chamber joined in fluid communication with a feeding device, and a dosage form unit placed within the formulation chamber. The dosage form unit contains the desired beneficial agents to be added to the liquid enteral nutritional product. As noted by the identified patents, a variety of dosage form units are available for use with these apparatus and methods, including conventional osmotically-driven delivery devices for sustained delivery of a beneficial agent.
One such osmotic delivery device is disclosed in U.S. Pat. No. 5,318,558, which is directed to a pump-type, controlled-release dosage form unit, or delivery device. Generally, the device includes a cylindrical enclosure containing the beneficial agent at one end portion and a piston driven by an osmotic engine at the other end portion. A small orifice is formed in the enclosure, preferably by a laser beam drill, at the end opposite the osmotic engine. In this manner, the beneficial agent is forced from the enclosure through the orifice upon activation of the osmotic piston.
An alternative osmotic dosage system with a sustained release dosage is disclosed by U.S. Pat. No. 5,324,280, wherein the beneficial agent is enclosed within an inner wall surrounded by a layer of hydro-active material that is entirely confined within an outer wall. Osmotic pressure resulting from expansion of the hydro-active material forces the beneficial agent out through a passageway formed in the outer wall by a laser drill or the like.
As noted, each of these conventional osmotic drug delivery devices requires that an orifice or similar passage be drilled or otherwise preformed in an outer membrane. Such precision manufacturing techniques, however, can be both difficult and expensive to perform. Additionally, it has been found that such conventional osmotic drug delivery devices are not particularly efficient, especially when used for the delivery of a marker dye or the like.
Furthermore, it is often desirable to provide an immediate release of beneficial agent upon initial exposure to the liquid enteral nutritional product. To accomplish this immediate release, conventional osmotic delivery systems typically require that an outer layer or film of the desired beneficial agent be provided. In this manner, an initial amount of the beneficial agent can be released quickly upon dispersion within the liquid nutritional product, followed by a sustained release of the beneficial agent from the dosage form unit. The provision of an additional outer film of beneficial agent, however, increases the manufacturing and material costs of the drug delivery device.
As such, there remains a need for an improved dosage form unit capable of sustained delivery of the beneficial agent(s) contained therein.